For many years internal combustion engines of the gasoline type or "carbureted" type have been timed through the detection of an ignition spark delivered to the sparkplug for the number one cylinder. Typically, the instant of spark is detected through the use of an inductive clamp inserted around the sparkplug wire running to the number one cylinder. As the automobile ignition coil, or an equivalent capacitive circuit, discharges its current or voltage to the sparkplug, a sizable current is induced in the sparkplug wire that creates a magnetic field sufficient to allow its detection through the use of any of a variety of inductive coupling devices heretofore known in the art. The most common of such inductive pickup devices utilizes a clamp having two halves separably connected in scissor-fashion to form a doughnut-shaped core around the ignition wire. Once clamped together, the core acts as a current detector, with the ignition wire acting as a generator and the core serving to transform the current or voltage from the ignition wire to a secondary coil which is looped around the core internal to the clamp structure. Various engine diagnostic tasks can be performed with this signal. Most commonly, this signal is used to fire a strobe light of high intensity to illuminate the timing marks on the dynamic damper or other moving elements of the engine on which one or more timing marks are provided. Since a signal is generated in the inductive pickup during each combustion cycle, that signal is also typically used to drive a tachometer circuit and display to indicate engine RPM to the user. Often, both timing and engine speed are derived from the same inductive signal, since the timing specifications for most vehicles are calibrated for specific engine speeds. Induction timing in carbureted engines has become quite popular due to the availability of low cost strobe lights and tachometers for both the skilled mechanic and the general public. As such, the public has been accustomed to this type of timing for many years.
Diesel engines have heretofore been incompatible with conventional induction-type timing equipment and tachometers, for, unlike spark-fired engines, which have readily accessible electrical wires carrying up to 20,000 volts to the sparkplugs, diesel engines have no ignition wires whatsoever. Combustion occurs as a result of pressure within the cylinder and through the proper timing of fuel injection. But while conventional induction timing equipment has heretofore been inapplicable to diesel engine timing, the problem of timing in those engines is as important, if not more important, than timing in a spark-fired engine. If combustion does not occur at the proper time relative to the piston reaching its top-dead-center (TDC) position, then incomplete combustion and/or backfiring can occur. This gives rise to a lack of power, possible damage to internal engine components, decreased engine efficiency and mileage and an increased potential for pollution.
Therefore, timing equipment has been brought to the market by several manufacturers for the purpose of measuring the timing and/or speed of a diesel engine through its injection system. For example, U.S. Pat. No. 4,185,494 assigned to Creative Tool Company discloses a system which provides timing of injection through the use of a transducer coupled to the fuel line at the pump or injection nozzle of a diesel engine. In recent years it has also become popular to time the instant of combustion within the cylinder. A system of this type has been disclosed, for example, in the application of Dooley and Williamson, Ser. No. 357,638 filed Mar. 12, 1982 now U.S. Pat. No. 4,441,360 and in the application of Dooley et al, Ser. No. 351,662, filed Feb. 24, 1982 now U.S. Pat. No. 4,423,624. The signal for timing in that instance is taken from a screw-in piezoelectric device which replaces the conventional glowplug in the number one cylinder for timing purposes.
While the equipment of the foregoing type has been quite effective in providing proper timing for injection and/or combustion in a diesel engine, it has required mechanics and the general public to purchase entirely new instruments dedicated solely to the timing of diesel engines. These instruments have, in general, been complex and somewhat expensive. Moreover, their size has been considerable and has required additional space for their storage. A properly equipped mechanic, in other words, has had to maintain one set of timing equipment for carbureted engines and an entirely different set of equipment for diesel engines.
It is a general object of the present invention to overcome the drawbacks and deficiencies of the prior art. More specifically, it is an object of the present invention to provide timing apparatus utilizing existing timing components and instruments already developed for gasoline engines in the timing of diesel engines.
It is a further object of the invention to provide diesel timing equipment which is simple to use and less expensive to manufacture than timing equipment heretofore made for diesels.
It is another object of the invention to provide an adaptor which allows for the timing of diesel engines with a wide variety of existing timing devices of the inductive type, thus avoiding a duplication of equipment and expense for the mechanic or other members of the public already possessing inductive timing and tachometer equipment.
It is a further object of the invention to provide an adaptor which may provide both timing and RPM simultaneously in a manner heretofore only made possible through existing and far more expensive diesel timing instruments.
It is another object of the invention to provide an adaptor that allows conventional induction timing equipment to be used in conjunction with a variety of signal sources, including both injection-type transducers and combustion-type transducers, with substantially equal facility.